Does Reverse Osmosis Remove Microplastics? What to Know First

You finally decide to do something about your drinking water. You read a few reviews, and nearly every one says the same thing: if you are worried about microplastics, get a reverse osmosis system. Then you see the price, the extra faucet, and the line about wastewater, and you wonder if it is worth the trouble.

So, does reverse osmosis remove microplastics? Yes. Reverse osmosis is among the most effective ways to remove microplastics from tap water at home. It is not a perfect seal, and it has real trade-offs in cost, upkeep, and wasted water. Here is what the research shows, what most guides leave out, and how to decide if it is right for your home.

Does Reverse Osmosis Remove Microplastics? The Short Answer

Reverse osmosis, often shortened to RO, pushes water through a very thin plastic sheet called a membrane. Water passes through. Most of what is dissolved or floating in it gets held back and washed down the drain.

According to the University of Massachusetts Amherst, RO can remove many contaminants, including sodium salts, nitrate, lead, and fluoride. Those salts are individual dissolved molecules. A microplastic is a solid piece of plastic smaller than about 5 millimeters, and even the smallest nanoplastics are clusters of many molecules. A membrane that blocks salt should, in principle, block nearly all of them.

A 2023 review in Water Science and Technology came to the same view. It found that membrane technologies are the most effective and promising way to remove microplastics from water, and that ordinary treatment plants cannot fully remove them.

What to do: If your main goal is the fewest possible plastic particles in your glass, RO is the strongest home option to consider.

Is Reverse Osmosis Perfect? What Most Guides Leave Out

Many filter sellers quote removal rates of 99.9% or higher. Be careful with those numbers. We could not find a published study that measured how well home RO units under the sink remove microplastics in real kitchens. Most of the strong figures come from lab tests, large treatment plants, or simple reasoning about pore size.

There are also two honest caveats from the research:

• Some particles can slip through. A 2023 University of Toronto study in Polymers notes that microplastics have been found in water leaving full-scale ultrafiltration and RO systems. Membranes can have tiny flaws, seals can leak, and pieces can get past worn parts.
• The system itself is plastic. The membrane, housings, and tubing are made of plastic. The 2023 review flagged that plastic membranes may release some particles into the water they treat. How much this matters in a home unit is not yet known.

The UMass guidance puts it plainly: membranes cannot be certified to remove 100 percent of anything. That is true of every filter, not just RO.

What to do: Think of RO as a large reduction, not a guarantee. Good maintenance is what keeps it working near its best.

Reverse Osmosis vs Other Filters for Microplastics

The 2023 University of Toronto team tested three pour-through home filters in the lab. The filter with the finest membrane, with openings of about 0.2 microns (far thinner than a human hair), did the best job. A filter that used only activated carbon and ion-exchange beads, with no membrane at all, had the most trouble with plastic fragments. At several points in its life, the water coming out held more plastic fragments than the water going in. The authors suspect trapped particles built up and then broke loose.

That is the most useful lesson for shoppers: a physical barrier with very small openings matters more than the word "filter" on the box. Here is how the common choices compare.

For a full side-by-side of setups at different prices, see our guide to the best drinking water filtration setups for every budget.

What to do: If you use a pitcher today, check whether it lists a microplastics reduction claim. If it does not, a membrane filter or RO is the upgrade.

Does Reverse Osmosis Remove PFAS Too?

This is one of the best reasons to choose RO. PFAS, often called "forever chemicals," are man-made chemicals that last for a very long time in the body and the environment. The U.S. Environmental Protection Agency says the RO, activated carbon, and ion-exchange home systems it studied can greatly reduce PFAS levels.

The EPA also offers two cautions. Filters only work if they are maintained as the maker directs. And as of April 2024, PFAS certifications did not yet show that a filter removes PFAS down to the new federal drinking water limits.

What to do: If PFAS have been found in your local water, one RO system can address both concerns at once. Ask your water utility for its latest water quality report before you buy.

The Trade-Offs: Wastewater, Minerals, and Upkeep

Wastewater

RO needs to flush away what it removes. The UMass fact sheet says about four gallons of water go in to make one gallon of filtered water, so roughly 75 percent goes down the drain.

Minerals and taste

The same membrane that blocks plastic also removes most of the dissolved minerals, such as calcium and magnesium. Some people find RO water tastes flat. Many systems offer an add-on stage that puts some minerals back for taste. If you follow a diet your doctor manages, such as for kidney or heart health, ask before you change your main water source.

Maintenance

A typical under-sink system has a sediment pre-filter, a carbon pre-filter, the RO membrane, a storage tank, and its own small faucet. UMass advises following the maker's schedule, keeping a simple maintenance log, and testing your water at least once a year. A clogged or torn membrane needs to be replaced.

What to do: Before you buy, add up the yearly cost of replacement filters, not just the price of the unit. Put a reminder on your calendar for each change.

How to Choose a Reverse Osmosis System

You do not need to become a water engineer. Use this short checklist.

1. Look for NSF/ANSI 58 certification. This is the standard for RO systems. The EPA suggests checking the label, the maker's website, or the NSF website to confirm what a product is certified to reduce.
2. Check for a microplastics claim. Some filters are certified for microplastics reduction under NSF/ANSI 401, which covers particles from 1 to 5,000 microns.
3. Pick under-sink or countertop. Countertop units skip the plumbing. Under-sink units hide away and deliver more water.
4. Compare the waste ratio. It varies by model, and lower is better for your water bill.
5. Price the replacement filters. A cheap unit with costly filters is not a bargain.

Start Here: If You Only Do Three Things

1. Stop relying on bottled water. Filtered tap water is usually the lower-plastic choice. Our article on microplastics in bottled water explains why.
2. Use a filter with a real barrier. Choose a certified RO system or a fine membrane filter rather than relying on carbon alone.
3. Keep filtered water out of plastic. Store and carry it in glass or stainless steel, so you do not add back what the filter took out.

Water is one source among many. For the next swaps, see our guide to household plastics and what to replace first.

Where Sifts Fits

Cutting exposure at the source, like the water you drink every day, is the step that matters most. Some people also add an optional gut-support routine. Sifts is formulated with chitosan and other dietary fibers intended to support normal digestive and elimination processes as part of regular gut function.*

Sifts works in the digestive tract. It is not a substitute for a good water filter, and it does not remove particles from your blood or organs. Sifts contains shellfish-derived ingredients and is not for people with shellfish allergies.

What the Science Still Cannot Tell Us

We still lack good real-world tests of home RO units for microplastics and nanoplastics, so exact removal rates are uncertain. Labs also count particles in different ways, which makes studies hard to compare. The World Health Organization has called for more research on how microplastics in drinking water affect health. Treat the evidence as a reason for a sensible upgrade, not alarm.

Frequently Asked Questions

Bottom Line

Reverse osmosis does remove microplastics, and it is one of the strongest options you can put in your home. It is not perfect, and it costs more in money, upkeep, and water than simpler filters. Choose a certified system, change the filters on schedule, and keep your filtered water in glass or stainless steel. If RO is not practical, a fine membrane filter is a worthwhile step up from carbon alone.

Comparing options at different prices? Read our guide to the best water filtration setups for every budget.

Sources: UMass Amherst, reverse osmosis treatment of drinking water supplies; Water Science and Technology, review of microplastic removal by membrane technologies, 2023; Polymers (University of Toronto), microplastic removal from drinking water using point-of-use devices, 2023; U.S. EPA, identifying drinking water filters certified to reduce PFAS; Water Conditioning & Purification, NSF standards for microplastics reduction, 2025; Environmental Science & Technology Letters, boiling tap water reduces nanoplastic and microplastic intake, 2024; Ohio State University, some bottled water worse than tap for microplastics, 2026; World Health Organization, microplastics in drinking-water, 2019.